Our licensing server should recognize that it's still the same computer after you reinstall, however sometimes there are problems with Windows that cause our server to not recognize the computer after you make changes. But don't worry, this is easy to fix. After you reinstall your OS and all your plugins, open a plugin window for one of your PA plugins. You'll need to re-enter your login info. After you do that, go to Manage Devices and check to see if you computer is listed twice. If it is, just click "Deactivate" for the older machine. If you can't tell which is the older one, just deactivate everything. Then re-authorize your plugins again, and then you should be properly authorized.